Safe Viewing Techniques

Safe Viewing Techniques

There are two safe ways to observe the partial phases of a solar eclipse. One way is to purchase a professionally manufactured solar filter (or "eclipse viewer") from a reputable source. These viewers are made with optical-grade filters that are designed to protect your eyes from damage by the visible and infrared wavelengths of the Sun.

The other way, with does not involve looking directly at the Sun, is to viewing the image of the Sun projected onto some surface; the image can be focused by having the sunlight pass through a pinhole. This is the same effect seen when the light from the partially eclipsed Sun shines through the leaves of a tree, creating tiny crescent images in the shadow on the ground. The diagram below illustrates how to build and use a simple pinhole projector. This is the safe and recommended way to observe the passage of the Moon across the face of the Sun during the partial phases of a solar eclipse. (If the eclipse is televised, it would also be safe to view it on the TV screen.) And don't forget: during the few minutes of totality it's OK to look directly at the Sun's corona.

View diagram of Building and Using a Pinhole Projector (79k)

You might find it interesting to see how you would judge the degree of darkness during totality. Scientists in the past, before sensitive light-measuring instruments were available, carried out elaborate experiments to obtain some measure of the darkness. Comparisons were made to candlelight, moonlit nights, twilight, etc. Reports were given on the readability of instrument dials and various sizes of print. One experimenter even proposed that the opening and closing of plant leaves and blossoms be used as a gauge of the relative darkness in the Moon's shadow. In general, it is darker nearer the center of the path of totality and in clearer weather. (Clouds scatter light.) You may also want to observe shadow bands. Put up a flat white sheet or screen at least three feet wide facing the Sun and look closely for the faint ripples of light a few minutes just before and just after totality.

** Material adapted from ECLIPSE by Bryan Brewer ($14.95 plus S&H). ECLIPSE Book Order Form. **

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